Brake booster



T. P. CHASE BRAKE BOOSTER Sept. 19, 1939.

Filed oct. 1, 1937 nventor fiese Patented Sept. 19, 1939 BRAKE BOOSTER/l Theron VI. Chase, Detroit, Mich., assignor to `Gleneral MotorsCorporation, Detroit, Mich., a corporation of Delaware ApplicationOctoberl, 1937, Serial No. 166,745

` 6 Claims.

It has been proposed in the past to lessen the manual effort required toapply the brakes of vehicles by the resort to other sources of powerunder the control of the operator. The present invention has thatpurpose for its major object.

As more' specific objects, the invention seeks to attain the majorobject by hydraulic mechanism which shall function efficiently, whichshall embody the well-known follow-up action and which shall be simpleand comparatively inexpensive.

Other objects and advantages will be understood from the followingdescription:

Accompanying this description is a drawing illustrative of oneembodiment which the inventive idea may assume.

In the drawing:

Figure l is a view of amotor vehicle in side elevation,V the view beingpartly broken away to show a portion of the brake system.

Figure 2 is a view in elevation, partly broken away and in section of anaccessory deviceWhich I propose to assemble alongside'the change speedmechanism to provide Ythe servo device which is to supplement the manualeffort in applying the brakes. v

Figure 3 is a section on line' :3--3r of Figure .2.

Referring to the drawing for a better understanding of the invention, itwill be seen that the vehicle as a whole is identified by numeral 1, itswheels being marked 9. Associated with the wheels, preferably one foreach wheel, are brake drums II within which are brake shoes, not shown,the shoes to be suitably anchored and to be spread apart into frictionalcontact with the brake drums by cams or some equivalent means. Thedrawing shows a rock shaft I3 having upper and lower arms I5 and I1.Suitable cables I9, preferably within cable housings 2I are connected toarms I5 and I1 and extend to or into the brake drums and serve toactuate the shoe expanding mechanism. It is unnecessary to moreparticularly describe the details of the specific structure of the partsby which a counterclockwise rotation of shaft I3 spreads the brake shoesthrough the instrumentality of the cables. Such details may be varied asdesired and their specific form constitutes no part of this invention.

A sleeve 23 projects through an opening in the side wall 25 of thechange speed gear box. It may be secured in place by fastening means 21.

A shaft 29 is rotatably supported by the sleeve 23. Shaft 29 is drivenby gearing elements 3| and 33, the former on a transmission driven shaft(Cl. 18S-152,)

35 and the latter on the end of shaft 29. In order to secureuni-directional rotation of shaft 29, it may be assumed that shaft 35 isthe conventional counter-shaft of the change speed mechanism.

Rotatably supported adjacent the gear box and for rotation about butindependently of shaft 29 is a chambered housing 31, the housing beingclosed by a cover 39. The cover may be secured to the housing byfastening means 4 I'. The housing andv cover constitute a rotatablewinding drum. Keyed at 43 to the end of shaft 29 is a pump gear 45.VCrear 45 snugly lits the space between the housing and the cover.Meshing withand driven by gear 45 isv an idler gear 41, the shaft 49 vofwhich is journaled in recesses 5I of the housing and cover. The housingis formed internally with walls 53 and 55 which surround the gears therebeing an inlet at 51 between these walls and a discharge outlet 59. Theoutlet terminates with a seat 6I adapted to be engaged by a valve orclosure disc 63, thev disc being formed on the end of a lever rotatablysupported by a pivot axis 61 carried by the cover. Axis 61 extendsoutside the cover and to its outer endis vxed a lever 59. Journaled on ashort axialhub 1I of the cover is a lever 13, the latter being held inposition by a washer 15 and a threaded bolt 11. This lever 13 isconnected to lever 69 by a link 19. The manually operated brake pedal 8|is connected to the extreme end of lever 13 by a link 83. A ilexiblecable 85 is wrapped partially around the circular wall of housing 31between ribs 81 and 89 and it is anchored to the housing at 9|. Thecable extends to and is attached to the extreme end of lever I5.

The winding drum formed by the housing 31 and its cover contains asuitable hydraulic medium such as oil. While the vehicle is being driventhe gears 45 and 41 within their surrounding walls 53 and 55 constitutean oil pump. The oil enters at 51, flows around between the gears andthe walls and is discharged at 59. Figure 2 shows the operating systemin its idle position wherein the pump outlet is open. Suitable springmeans such as spring 93 serves to hold the valve 63 off its seat. If itbe desired to apply the brake, the pedal 8l is depressed. The rstresponse to the pedal depression is a rotation of the winding drumformed by the housing and the cover as the unit and the cable woundabout this drum functions to rotate rock shaft I3 whereupon the cablesI9 cause the shoes to engage the brake drums. This action occurs ratherthan a rotation of lever 13 independently of the drum resulting imV in aclosure of the outlet 59 for the reason that the movement of the brakeshoes. into contact with the brake drums oers less resistance than doesthe compression of spring 93. When, however, the pedal is furtherdepressed, the shoes which are now in contact with the brake drums,oifer greater resistance than the force required to overcome the tensionof spring 93. As a result of this difference in resistance lever 13rotates about the axis of the winding drum and through theinstrumentality of link 19 and lever 69, it moves the valve 63 againstits seat. Since the gear 45 is still being driven the reaction causesthe winding drum to rotate. Such rotation of the winding drum moreforcibly applies the brake shoes to the brake drums. In doing so, and ifit be assumed that the pedal 811 and lever 'I3 remain stationary, lever65 rotates about its axis and the valve opens. It can be again closed byfurther movement of the pedal 8|. In consequence the operation embodiesthe desirable succesive respense to progressive movements commonlyreferred to as a follow-up action. It will be readily seen also that ifthe engine is not operating the pedal can apply the brake directly byrotating the winding drum. It will rst take up the shoe clearance asbefore, it will then close the valve 63 upon its seat and furtherdepression of the pedal will again rotate the winding drum and forciblyapply the shoes.

It will be obvious also that the winding drum and cable may operate,through suitable mechanism, the master cylinder of a hydraulic brakesystem in the event that the invention is applied to a vehicle equippedwith hydraulically operated brakes.

Throughout the above description, the power or servo mechanism has beenexplained with reference to brakes. It should be explained that otheruses are possible.

I claim:

l. A power transmission, a power take-01T shaft driven thereby, a gearon said last named shaft, a winding drum housing said gear and rotatableabout the axis of said take-01T shaft, an idler gear supported by saidwinding drum in a position to mesh with said first-mentioned gear, saidwinding drum having an internal construction formed to constitute withsaid gears, a gear pump having an inlet and outlet, a valve to closesaid outlet,

let, a lever rotatable to move said valve, said lever journaled to saidwinding drum, a second` lever rotatable about the axis of said winding'drum, link means between said levers, manually operable means to rotatethe last-mentioned lever, a cable extending from said winding drumwhereby actuation of the manually operable means may close the pumpoutlet and whereby work may be done by the resulting rotation of thewinding drum acting through the cable.

2. A power booster adapted for the application of vehicle brakescomprising a rotatable winding drum, a connection from said drum adaptedto apply brakes, a gear pump within said winding drum, said pumpcomprising a driven gear and an idler gear, manually operable means toclose the outlet of said pump to effect rotation of said winding drum.

3. A power booster brake for vehicles comprising a change speedtransmission, a power take-off shaft driven thereby, a winding drummounted for rotation about the axis of said last-named shaft, a cableattached to said drum and means attached to said cable and operable toapply brakes, a gear pump within said winding drum including a gear onsaid take-ofi shaft and manually operable means to close the outlet ofsaid pump and to thereby effect rotation of said winding drum.

4. The invention defined by claim 3 together with yielding means toresist closure of the pump outlet whereby the manually operable meansmay function to rotate the winding drum prior to the closure of saidvalve.

5. The invention defined by claim 3, said manually operable meansincluding parts whereby the power servo device has a follow-up action.

6. The invention defined by claim 3, said manually operable meansincluding parts whereby the power servo device has a follow-up action,said parts including a lever pivoted to rotate about the axis of saidwinding drum, means to rock said lever, a lever pivoted eccentrically tosaid winding drum, a link connecting said levers a valve operablyconnected to said off-center lever and operable to close the outlet ofthe pump.

THERON P. CHASE.

